The present invention relates to a device and method for positioning a measuring head on a noncontact three-dimensional measuring machine.
Noncontact three-dimensional measuring machines are known in which a member is movable along three coordinate X, Y, Z axes of a first reference system of the machine, and carries a measuring head articulated with respect to the movable member and supporting a visual sensor comprising a television camera and a laser beam generator.
The camera picks up a three-dimensional space (e.g. a pyramid-shaped solid angle) having an optical axis of symmetry which intersects the axis of symmetry of the laser beam at a point (reference center) defining the origin of a second Xxe2x80x2, Yxe2x80x2, Zxe2x80x2 reference system of the visual sensor, the Zxe2x80x2 axis of which is aligned with the optical axis of symmetry of the camera. The image picked up by the camera comprises a two-dimensional image of the object in the measuring space, which image has a visible (laser) line formed by the laser beam intersecting the object, and is viewed by the measuring machine operator on a monitor.
By means of a processing device, the two-dimensional image picked up by the camera and the position in the two-dimensional image of the laser beam with respect to a reference position (conveniently a central position in the imagexe2x80x94image center) are analyzed automatically to determine the coordinates of points on the object with respect to the second Xxe2x80x2, Yxe2x80x2, Zxe2x80x2 reference system of the visual sensor; and the measurement is then related by the processing device to the first X, Y, Z reference system of the measuring machine.
A major drawback of known measuring machines is encountered when positioning the measuring head, i.e. when moving the measuring head into position close to the object to be measured. That is, the measuring head is moved manually by means of a control device, in particular a joystick, which generates a signal to move the measuring head along the three X, Y, Z machine axes, whereas the image observed by the operator on the monitor is that picked up by the visual sensor and oriented according to the three Xxe2x80x2, Yxe2x80x2, Zxe2x80x2 axes which do not correspond with the X, Y, Z machine axes. Moreover, since the operator can only control the measuring head along the X, Y, Z axes and does not know the relationship between the Xxe2x80x2, Yxe2x80x2, Zxe2x80x2 and X, Y, Z axes, considerable difficulty is encountered by the operator in positioning the measuring head using the manual control device and the image shown on the monitor.
It is an object of the present invention to provide a measuring device enabling the measuring head to be moved easily as required and to be set to a predetermined position with respect to the object using the image of the object on the monitor.
According to the present invention, there is provided a device for positioning a measuring head of a noncontact three-dimensional measuring machine, as described in claim 1.
The present invention also relates to a method of positioning a measuring head of a noncontact three-dimensional measuring machine, as described in claim 9.